cheney



G. R. BLODGETT, M; E. CHENEY AND ,R. T. HURLEY.

SPARK PLUG.

'APPHCAUON FILED OCT-22.1921- I 1,399,375, Patented Dec. 6, 1921.

2 SHEETS-SHEET 2.

spark plugs.

UNITED ST TES ,rA- EN oFFICE.

GEORGE n. 31.0nenw1r, ANnMosEsE. CHENEY, or BROOKLYN, AND ROY T. HURLEY,

- orNEwYonmrLY." I

i I SPARK-PLUG.

Application fi1ed October22, 1921 Serial No. 509,483.

To all to 710m it may concern:

Be it known thatwe, GEoRGE R. BLODGETT, Moses E. CHENEY, and ROY Tal lURLEY, citizens of the United States, the said Brionenrr and CHENEY residents of Brooklyn, county of Kings, and State of New York, and the said HURLEY a resident of Bronx, county of Bronx, and State of New York, have invented new and useful Improvements in Spark-P111 gs, of which the @ur invention relates to improvements in with cylinders of internal combustion engines of low compression ratios which shall be better adapted. for the particular uses to which they are to be put and'to produce spark plugs of the above character more efiicient and durable and less liable to car bonization and pre-ignition in use than has heretofore been possible. It consists of the novel devices herein set forth.

Heretofore many attempts have been made to overcome the troubles of carbonization and pre-ignition so frequent in the use of spark plugs of the above general character. But so far none of these attempts have been entirely satisfactory or successful in overcoming the troubles. While many expedicuts have been suggested, more or less successful under certain specified conditions,.

none of them have resulted in the production of spark plugs uniformly and durably freef from these troubles.

e have discovered thatthere 1s a close relationship exlstlng between the volume of r the space within the spark plug surrounding the electrode and adjacent parts, into which space the gas flows from the cylinder and 1n which it is burnt, the area of the walls of such space effective to receive, maintain and dispense heat, themanner and extent of admission of gas into the space, and the com pression ratio of the'engine cylinder with which the spark plug is tobe used, and that, if the proper arrangement and proportions are secured in the manufacture of the spark plugs in these factors or particulars, the resulting spark plugs produced will be well adapted for the particular uses to which they are intended to be put, will be I more durable and will functionbetter than ordi nary spark plugs and' that over a;.much wider" range of compression ratios and under Specification of- Letters Patent.

It has for its object to bring about the production of spark plugs for use Patented Dee-6, 1921.

. much. greater changes in load conditions,

will be freer? from liabilityto carbonize or ;1

gasintroduced into I the space within the spark plug will be brought into, the, very best condition for combustion and the arts 7 P of the spark plug with whiohthegas comes lnto contact will be under ordlnary runnlng conditions brought ,into and maintained "within the proper limits. oftemperature to produce the best results, neither low enough to permit 'carboniz ation or highenough-to cause PIe-Ignlt1011. The gas itself will be broughtintothe most favorable condition," bothasto compression and complete vaporfization of the fuel, for complete combustion; thus securing the highest efiiciency'without leaving harmful products of combustion on theelectrode, insulation or other parts. I

"lVe" have found that ill' englne cylinders there are two generalxclasses of compression ratio, one that, for convenience, we termhigh compression}? including englne cylinders such as areused for aviation purposes, where compression is relatively h gh .and

speed constant, and low c0mpressionratio, as in engine cylinders adapted for automojbiles and marine purposes, Where the compression 1s lower and the. speed variable;

In this specification and claims we use the terms high and 10W QOIHPIQSSlOIlIfllQlO 'inthis. general sense, 'lhepresent applicatlon is addressed spec fically to spark plugs for use in low compressionratio engines.

In the accompanying drawings forming part hereof, we have illustrated our im- 'provement in its preferred forms for vary- .g1-eater part of the spark plugs. Fig. 3 represents a centra-l section throughan engine conditions. Referring-Ito the drawings cylinder havinga low compression ratio, 7

, suitable for use with automobiles. v

. Referring to Fig.1, 1 represents the shell of the spark plug, 2 a central electrode, 3 the/insulation surrounding it, 4 the other electrode, and 5 a gasket "between theyinsulatiou ed t e she' l All th r the spark plug are not shown in detail.

to cause pre-ignition.

6 is apart of the insulation protruding down= ward towardthe end of the central electrode 2. 7 is a space formed within the lowerpart ofshell 1, the walls of the space consisting of "the interior surfaces of shell 1- and the exterlor surfaces of the lower part of electrode 2 and of protruding portion 6 of the insulation. This space is of'course filled with gas at each operation of the engine cylinder, which gas 1s exploded at the proper time during such operation. We

have discovered that this space and the area of the surfacesof its surrounding walls effectiye :to receive, maintain and dispense heat,and the cross-sectional area of the orifice 8, should be proportioned and arranged with reference to the compression ratio adapted to be developed undriordi- .nary running conditions in the engine cylv inder with which the sparl: plug is adapted to-be used, andwhen the proper relationship" of the Volume of. such space, and the.

effectiye heat area of the surrounding walls and the cross-sectional area of the orifice to one another and to thesaid compression ratio is obtained, the electrode and itsadjacent parts, and the walls of the shell will iiider ordinary running conditions be kept "within a proper range of temperature, properly to conditionthe gas forthe most complete combustion possible at the proper ,moment, 6., to bringflit toand maintain it withinthe proper limits .of temperature, on the one hand above the 'carbonization point, 5. 6., not low enough .to permit carbonization, and on the other hand below the pro-ignition point, z. 6., not high enough In general, the volume of such space and the effective heat area of its surrounding walls should be decreased as the compression ratio increases and increased as that ratio decreases, al-

though the rate-of such decrease or increase s not exactly proportioned to the rate of increase or decrease in the compression ratio. r

Generally speaking, the orifice ,should' be more or less restricted, depending upon the compression ratio. In general, as the coinpiession ratio becomes higher, the orifice should become larger in crosssectional area, although this does not exactly vary in direct. proportionto the rise in compression ratio. in other words, speaking generally, if the compression ratio lshig'h, the area of the orifice should be larger and, if the compression 15 lower, the cross-sectional area of the, orifice should be less.

The area of the walls of the space, referred to herein as effective area .or effective heat areal, refers not tothe total actualphysical surface as merely measured inlsquare centimeters but'to the total of the heatin'g capacityof those walls. These lat alls This/for conciseness we tinel salts or pyrorneters.

in spark plugs are composed'of a number of different substances, such as the inside walls of the shell of metal, the exterior .Wallsof the spindle and electrode usually of a different metal, the exterior walls of insulating material, which may Vary in different plugs etc. These substances have different heat capacity, conductivity, etc., and durng normal running conditions one part will run hotter than another part, for example,

and thus impart more heat to the uneX ploded gas inthespace. There are thus two factors entering into the effective heating workdone by these different parts of the walls of the space, one the actual physical area of apart and the other the relative capacity of the part to absorb, hold and glue out heat" to such gas. Manifestly the area or effective heat area and each of the terms is used with this meaning throughout the specification andrclaims. The actualtemperature of any of the parts under normal running coneitions can be ascertained in .anyof the waysknown to those slrilledin the art, such as bythe use ofsen- To givean lllustration of, the method of computing the effective area of any part such as the surface of the central electrode, we will assume that the actual physical surface of the electrode inany particular case is one square centimeter. The actual temperature under normal running conditions ofthe surface of the electrode is determined to be 1900 F. absolute and the temperature required to condition the fuel in this particular case is 1135 i absolute, then theeifectiye heat- .ing surfaceof the electrode would be the,

product of its area 1 by the ratio of which. is 167+ square centimeter. The effective area of each of the other parts is computed in the same way.

Figs. 1 and 2 illustrate spark plugs ad ipted to be used with engine cylinders of a relatiyely'low degree of compression ratio. The spark plug of Fig. 1 is adapted to be used with engine cylinders of automobiles,

and that of Fig. 2 with engine cylinders of .marine engines, in which the compression ratio is usually stilllower than that of engine cylinders adapted for automobilense.

The corresponding parts .ofthe spark plug :of Fig 2 are nuinheredto correspond with similar parts of the sparkplug of Fig.1.

I El -eit w be reta l-tha a pac 7 is larger or has a larger volume than that in Fig. 1, and the surface area of the parts constituting the walls of the space in Fig.

2 is larger than that of the corresponding parts in Fig. 1. The orifice 8 of the spark plug of Fig. 2 has a cross-sectional area of less size than that of Fig. 1. In Figs. 1 and 2, the restricted opening 8 in each case is shown as made by means of a cap 10 having a restricted circular central opening.

Fig. 3 is a central section throughan engine cylinder having alow compression ratio and represents an engine cylinder such as the spark plug of Fig. 1 is adapted to be used with. At its upper end it is shown con- -nected to a spark plug similar to Fig. 1.

Fig. 3 is drawn diagrammatically to represent the range of displacement and corresponding compression ratios in low ratio compression cylinders. For this purpose-the right half of the figure represents substantially about the highest limit ofdisplacement or ratio of compression, and the left hand part of the figure represents ab'out'the lowest limit of displacement and the lowest limit of compression ratio in low compres sion cylinders. In each half 11 represents the lower end in eachcase-of the cylinder and the'distance between that in cachinstance and the dotted line 12represents the lengthof stroke of the piston, and the distance from the dotted lines to the 'upperend of the cylinder represents in each instance the compression chamber of the'cyl inder. In, one case the stroke is 4 inches, and in the other 5 inches. In theleft hand half the compression chamber is 1.6 inches in length and in the right hand halfit is 1.25 inches in length. 13-represents theouter walls of the cylinder, 14 the inner walls, and 15 an intervening space' for a cooling fluid. (The other parts of the cylinder and its connections are not shown in detail, being of any ordinary construction and forming no. part of our lnvention. r I

While the limits of compressionratio "and corresponding limits of volume of the space surrounding the electrode and adj acent parts and of the effective area of the surface of the walls ,of said space cannot be stated exactly for the different classes of low compression cylinders,we have found that under ordinary running conditions they are about as follows: For low compression engines adapted for automobile and marine use,

namely, those in which the. compression ra-,

tio under ordinary running conditions will range lower than about 5 to 1, the'Elimits will generally range from about 5 to 1 to about 3 to 1, the volume of the space should range from about 1.25 cubic centimeters to about 1.75 cubiccentimeters, and the surface of the walls of the space should range from square centimeters. one application of our-improvement is to take any specific core and shell constr ctio'n of spark plug, meaning by that a special an rangement, form, shape, si.ze,"etc., of 'cen- '7 Restriction ofithe orifice and especially in "proper relationship to the other factors re ferred to above, assists in securing the proper amount ofgas'in the spark plug on 1 each operation and in bringingthat gas to the proper' temperature and; condltion for explosion. Where an op'ening'to a'sparl;

plug is unrestricted there are apt to be devi 'ous currents interfering with bringing the gas into proper condition I for 625131081011,

While with a restrictedopening there is a fuel fluid. is more thoroughly brought into contact with the walls of the space inside of the plug. tending to bring it into proper condition;

positive swirling flow inward before eXplosion and outward'after explosion, and the The restriction of the orifice tends also to separate the spaceinside' of the spark plug from the space inside of the cylinder more than wouldotherwise be the case, thus preventing too great and sudden rushes from the cylinder of cold gas before explosion and of intensely heated gas after explosion,

and also permitting the gas Withinthe space in the spark plugqtobe brought intobetter condition.foricombustion than is possible with the: gas in the cylinder generally.

In low compression engines for automobile and marine use where the compression ratio varies as above stated-thecross-s'ectional area of the orifice should vary'from about :20 squa' centimeters to about .10

tral spindle, surrounding insulation, central electrode and surrounding shell, etc,

and vary or adapt the orifice to cause such spark plug to become fitted for use with any desired low compression ratio. of engine cylinder, orto adaptit so that it will within said limits cover wide range of compression ratios. While this can becarried out under the general principles laid down above, we, have discovered that the best cross-sectional area of orifice such in stances cited can he derived from the following formula, namely, 0:15a in which ticular core and shell construction can be determined by taking two spark plugs of the same core and shell construction except that the orifices in thetwo cases will Vary. The two plugs are then tested uponcylinders of different compression ratios until in each case the compression ratio is determined with which the spark plug gives best results. Such tests arewell known to those Skilled in the art and need notbe described in detail except-to say thatin makingsuch tests the range of compression ratios, over which the spark plug, in each case,will :func tion withoutcarbonization or pre-ignition is determined and then the compression ratio,

substantially mid-way between the lower and upper limits of such range, is taken as that at which, under normal running conditions, the spark plug gives the best results; The phrase gives best results is used throughout the specification and claims with this meaning.

The values of all the factors now being known, the netvalue of O can be determined in the original formula, O Kr.

By adding to the said net valueof O the cross-section of the central electrode and the projected surface of the ,side electrode, the gross area and diameter of orificecan be obtained.

Our improved spark plugs are durable,;efficient, not liable to carbonizationor preignition in use even over a wide range of compression ratios and load conditions.

What we claim as new and desire to secure by Letters Patent is: p 7 1. In a spark plug adapted for use in connection with cylinders of internal combustion engines having a compression ratio lower than 5 to l the'combination of an electrode and a shell provided with a space, to be filled with gas from the cylinder,sur-

rounding the electrode and adjacent parts,

and a restricted orifice adapted to connect the space with the cylinder of an engine, the relative proportions of the volume of the space within the spark plug and the effective area of surface of the walls of said space and the cross-sectional area of the orifice to one another being substantially as follows: the volume of said space being within about 1.7 5 cubic centimeters to about 1.25cubic centimeters, theeffective area of surface of the walls of said space being withinabout 43. square centimeters to about 20. square centimeters, and the cross-sectional area of the orifice being within about 0.10 square centimeters to about .20 square centimeters.

2. The combination of a cylinder of an internal combustion enginehaving a low compression ratio, a spark plug fitted into a wall of the cylinder, having an electrode and a. shell provided with a space, to be filled with gas from the cylinder, surrounding the electrode and adjacent parts, and a restricted orifice adapted to connect the'space with the cylinder, the relative proportions of the volume of'the space within the spark plug and the effective area of surface of-the walls of said space and the cross-sectional area of the orifice to one another being substantially as follows: the volume of said space being within about 1.-7 5 cubic centimeters to about 1.25 cubic centimeters, the eifective area of thesurface of the walls of said space being within about 43. square centimeters to about 20. square centimeters, and the crosssectional area of the orifice being within about 0.10 square centimeters to about 0.20 square centimeters. 1

3. In a spark plug adapted for use with a specific low compression ratio or range of low compression ratios of cylinder of internal combustion engines, the combination 'of aspecific core and shell construction forming a space around the electrode and adjacent parts of a specific volume and having a specific effective area of surface for the walls of said space, and a restricted orifice for said space of a cross-sectional area of the value of O in the formula O:Kr,where K and n are constants depending uponthe said construction of core and shell, and are de terminablefrom two spark plugs of the said construction of core and shell but difiering form each otherin cross-sectional. area of orifice, when each spark plug is used with the compression ratio adapted to give the best resultsfor said spark plug.

4:. The combination of a cylinder of an m- .ternal combustion engine of a specific low .compresslon ratio, a spark plug fitted into cross-sectional area of orifice, when each spark plug is used with the compression ratio of cylinder adapted to give the best re sults for said spark plug.

In testimony whereof, we have signed our names to this specification.

GEORGE R. BLODGETT. MOSES E. CHENEX. ROY T. HURLEY. 

